/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General
** Public License as published by the Free Software Foundation.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
** Library General Public License for more details.  To obtain a
** copy of the GNU Library General Public License, write to the Free
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** map073.c
**
** Mapper #73 (Konami VRC3)
** Implementation by Firebug
** $Id: map073.c,v 1.2 2001/04/27 14:37:11 neil Exp $
**
*/

#include <noftypes.h>
#include <nes_mmc.h>
#include <nes.h>
#include <libsnss.h>
#include <log.h>

static struct
{
    bool enabled;
    uint32 counter;
} irq;

/**************************/
/* Mapper #73: Salamander */
/**************************/
static void map73_init(void)
{
    /* Turn off IRQs */
    irq.enabled = false;
    irq.counter = 0x0000;

    /* Done */
    return;
}

/****************************************/
/* Mapper #73 callback for IRQ handling */
/****************************************/
static void map73_hblank(int vblank)
{
    /* Counter is M2 based so it doesn't matter whether */
    /* the PPU is in its VBlank period or not           */
    UNUSED(vblank);

    /* Increment the counter if it is enabled and check for strike */
    if (irq.enabled)
    {
        /* Is there a constant for cycles per scanline? */
        /* If so, someone ought to substitute it here   */
        irq.counter = irq.counter + 114;

        /* Counter triggered on overflow into Q16 */
        if (irq.counter & 0x10000)
        {
            /* Clip to sixteen-bit word */
            irq.counter &= 0xFFFF;

            /* Trigger the IRQ */
            nes_irq();

            /* Shut off IRQ counter */
            irq.enabled = false;
        }
    }
}

/******************************************/
/* Mapper #73 write handler ($8000-$FFFF) */
/******************************************/
static void map73_write(uint32 address, uint8 value)
{
    switch (address & 0xF000)
    {
    case 0x8000:
        irq.counter &= 0xFFF0;
        irq.counter |= (uint32)(value);
        break;
    case 0x9000:
        irq.counter &= 0xFF0F;
        irq.counter |= (uint32)(value << 4);
        break;
    case 0xA000:
        irq.counter &= 0xF0FF;
        irq.counter |= (uint32)(value << 8);
        break;
    case 0xB000:
        irq.counter &= 0x0FFF;
        irq.counter |= (uint32)(value << 12);
        break;
    case 0xC000:
        if (value & 0x02)
            irq.enabled = true;
        else
            irq.enabled = false;
        break;
    case 0xF000:
        mmc_bankrom(16, 0x8000, value);
    default:
        break;
    }

    /* Done */
    return;
}

/****************************************************/
/* Shove extra mapper information into a SNSS block */
/****************************************************/
static void map73_setstate(SnssMapperBlock* state)
{
    /* TODO: Store SNSS information */
    UNUSED(state);

    /* Done */
    return;
}

/*****************************************************/
/* Pull extra mapper information out of a SNSS block */
/*****************************************************/
static void map73_getstate(SnssMapperBlock* state)
{
    /* TODO: Retrieve SNSS information */
    UNUSED(state);

    /* Done */
    return;
}

static map_memwrite map73_memwrite[] = {{0x8000, 0xFFFF, map73_write}, {-1, -1, NULL}};

mapintf_t map73_intf = {
    73,             /* Mapper number */
    "Konami VRC3",  /* Mapper name */
    map73_init,     /* Initialization routine */
    NULL,           /* VBlank callback */
    map73_hblank,   /* HBlank callback */
    map73_getstate, /* Get state (SNSS) */
    map73_setstate, /* Set state (SNSS) */
    NULL,           /* Memory read structure */
    map73_memwrite, /* Memory write structure */
    NULL            /* External sound device */
};

/*
** $Log: map073.c,v $
** Revision 1.2  2001/04/27 14:37:11  neil
** wheeee
**
** Revision 1.1  2001/04/27 12:54:40  neil
** blah
**
** Revision 1.1  2001/04/27 10:57:41  neil
** wheee
**
** Revision 1.1  2000/12/30 06:35:05  firebug
** Initial revision
**
**
*/
